The present invention relates to devices for testing the presence of materials in air and other gases in general and, in particular, to a new and useful gas testing tube and method of measuring gas, vapor and aerosol components in an air sample.
A comprehensive assortment of test vials for quantitative rapid analysis of gases, vapors and aerosols in air in the range of the MAK number, the lower limit of inflammability and for technical gas analysis are available. For application, the tips of the test vials are broken off, the test vial is inserted into the gas detection pump and, with this, the prescribed gas volume is suctioned through the reaction layers. Most test vials are graduated tubes, where the indicator layer becomes discolored over a length, dependent upon the gas concentration. There are also test vials with a color comparator layer where, upon the reaction, a color comparison is made.
Test vials which contain one or even several breakable ampoules with liquid or gaseous reagents are also known. Here, the test vial is breakable in the area of the ampoule, which is covered over with a hose sleeve.
The ampoules provide the possibility of storing liquid or vaporized reagents in the test vial, without these materials coming into contact with the other granular fillings during the storage period. For purposes of application, the test vial is broken at the breakable area, always at the correct point in time for the reaction, whereby, the ampoule also breaks, and its contents empty into the interior of the test vial. The hose sleeve prevents the test vial from falling apart.
In one known procedure for the determination of chlorvinyl-arsenic (lewisite) by means of a test vial, the air to be examined is passed over a surface-active layer, such as silica-gel, which contains traces of water. The arsenic compounds formed from the chlorvinyl-arsenics are then brought into contact with nascent hydrogen, and the aresenic-hydrogen compounds thus formed are then detected by known procedures. For the production of nascent hydrogen, a metal powder or metal dust is placed in front of the surface-active layer and the ampoule containing sulphuric acid. Zinc dust, aluminum dust or similar substances can be used as the metal layer.
On breaking of the ampoule, sulphuric acid vapor penetrates the metal layer. The test vial is used as follows:
After breaking the tips, the air to be tested is suctioned into the test vial. If the air contains lewisite, this is broken down in the decomposition layer through the formation of arsenic and arsenic compounds. The ampoule is then broken and some more air is suctioned through the vial. This permits the sulphuric acid vapor to react with the metal. The hydrogen thus formed reacts with the arsenic in the presence of lewisite, which then leads to a discoloration in the known manner. The discoloration occurs on a solid carrier. The color substance formed occurs on this carrier in a large dilution, so that the color intensity in very small contaminant concentrations in the test air during a normal air sample flow can no longer be evaluated (See German Patent No. 1,140,749).